1. Field
This invention relates to signal processing. In particular, the invention relates to echo cancellation.
2. Description of Related Art
Echo is generally undesirable in telephony. Echo is caused by a number of sources. These include multiple reflections of the signal from the loudspeaker back to the microphone, direct acoustic coupling between the loudspeaker and the telephone, and ambient noise. Echo cancellation is a technique to reduce the undesirable effects of the echo. The echo canceller estimates the impulse response of the echo path and generates an estimate of the echo. The estimated echo is then subtracted from the near-end signal. Typically, an adaptive filter is used to estimate the echo because the echo path is usually unknown and randomly time-varying.
An existing technique for echo cancellation is the normalized least mean squares (NLMS) method. This method attempts to minimize the expected value of the squared error. However, the NLMS method has a number of disadvantages. One significant disadvantage is its slow convergence rate for color inputs. Furthermore, when the echo channel has sparse multi-path channels, the NLMS method may not provide proper results.
Therefore, there is a need to have an efficient technique to perform echo cancellation having a convergence rate faster than the NLMS method in sparse multi-path channels.